A vehicle is disclosed, for example, in DE 198 21 451 A1. The rails are connected fixedly to the chassis. The driver's seat is mounted over a region of movement on the rails, for example via wheels, which can be driven by electric motor. By means of this configuration of the seat mounting and of the adjustment region, the center of gravity of the loaded vehicle is situated relatively high up, which may result in critical handling on a flat, uneven underlying surface.
Physically disabled people very frequently use electric wheelchairs to travel along paths and roads. For outside, there are specially designed vehicles which have a more powerful drive and more stable running gear dimensions than vehicles designed primarily for inside, so that the vehicles can be used also to cope with relatively uphill and downhill sections. When traveling downhill, there is the problem that the person using the wheelchair has a tendency, as a consequence of the changed angle with respect to the axis of gravitational force, to slide on the seat surface of the driver's seat. As a consequence of their disablement, the drivers of electric wheelchairs frequently have reduced muscle function and therefore cannot physically counteract the changed center-of-gravity conditions. Therefore, the person either has to be fixed on the seat via a belt system, which is then associated with a high pressure loading of the fabric situated under the belt or a seat angle adjustment means has to be provided by means of which the inclination of the driver's seat with respect to the chassis can be set. Before traveling downhill, the seat then has to be inclined manually out of the normal position and, after the downhill section is finished, has to be brought back again into the normal position. The drivers frequently require external assistance for this. In addition, the actuation of the manual seat adjustment has to take place at a standstill, which means that the adjustment process is correspondingly costly.
EP 0 829 247 A2 describes a wheelchair which comprises a chassis and a seat mounted on the chassis, in which the inclination of the seat surface can reach any desired position by means of adjusting elements. An inclination measuring device controls the adjusting elements, so that the inclination of the seat surface can be kept horizontal even if the wheelchair is passing over uneven terrain.